الفهرس 
Optical properties of the corneaOnly 14 pages are availabe for public view
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Abstract
Refractive surgical procedures attempt to improve unaided visual acuity and correct spherocylindrical errors by reshaping the central cornea which is the most powerful refractive element of the eye and the easiest to access surgically.
Refractive surgery induces an increase in higher-order aberrations (HOAs) and may lead to visual losses that are detected under scotopic (low light) conditions and by low-contrast visual acuity testing. The increases in HOAs are known to be responsible for patients complaints of glare, halo and disturbances in night vision.
Higher-order aberrations due to a large difference between the treated and the non – treated cornea, or a large pupil diameter in relation to treatment zone diameter can be reduced by enlargement of the optical zone reducing halos and glare.
The FOZ was an important parameter in determining visual quality. It is important to differentiate between FOZ and the ablation zone. In order to minimize aberrations, the FOZ should be comparable or larger than the entrance pupil as light passing outside the FOZ tends to cause aberrations reducing the two point discriminability of the retina.
Therefore, the evaluation of the functional optical zone (FOZ) can help us in understanding the changes that occurred postoperatively as changes in corneal shape, and night vision disturbances.
In order to improve the results and patient satisfaction, it is important to consider the postoperative FOZ and preoperative pupil diameter also we should reconsider the amount of attempted correction.
Patients undergoing LASIK procedures display an increase of night vision disturbances even when the results of the surgery are considered entirely satisfactory. Secondary astigmatism and other higher order aberrations are significantly correlated with night vision disturbances so the attempted correction should be always noticed. Further studies will be important to declare the degree of secondary astigmatism induced by toric ablations.